unit 4 Central Neural Mechanisms in Movement
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Questions and Answers

What role do sensory feedback loops play in movement?

  • They solely depend on emotional responses.
  • They initiate movement directly.
  • They help adjust movements based on sensory information. (correct)
  • They are not involved in movement.

    • Motor learning results in a deterioration of motor performance over time.

    False

    What neurotransmitter is critical for modulating movement initiation and control?

    dopamine

    The ______ pathway is responsible for initiating quick, precise movements.

    <p>direct</p> Signup and view all the answers

    Match the following neurological disorders with their characteristics:

    <p>Parkinson's disease = Disruption of movement initiation Huntington's disease = Involuntary movements and cognitive decline Cerebellar ataxia = Loss of coordination and balance Stroke = Deficits in movement execution</p> Signup and view all the answers

    Which neural circuit is mainly involved in complex and adaptable actions?

    <p>Indirect pathway</p> Signup and view all the answers

    Imbalances in neurotransmitter systems can impact motor functions.

    <p>True</p> Signup and view all the answers

    What is a key factor in the strengthening of synaptic connections during practice?

    <p>repetition</p> Signup and view all the answers

    ______ feedback pathways provide ongoing sensory information about the body's position and movement.

    <p>Sensory</p> Signup and view all the answers

    Which of the following is not a neurological disorder that affects movement?

    <p>Epilepsy</p> Signup and view all the answers

    Which region of the brain is primarily involved in planning and executing voluntary movements?

    <p>Motor Cortex</p> Signup and view all the answers

    The supplementary motor area (SMA) is primarily responsible for reflexive movements.

    <p>False</p> Signup and view all the answers

    What role do the basal ganglia play in motor control?

    <p>They regulate force and speed of movements, inhibit unwanted movements, and contribute to initiation of actions.</p> Signup and view all the answers

    The ______ is vital for motor learning and coordination.

    <p>cerebellum</p> Signup and view all the answers

    Match the brain regions to their primary functions:

    <p>Motor Cortex = Planning and executing voluntary movements Basal Ganglia = Regulating force and speed of movements Cerebellum = Motor learning and coordination Premotor Cortex = Planning and sequencing movements</p> Signup and view all the answers

    Which of the following factors can influence motor plans?

    <p>Motivation and attention</p> Signup and view all the answers

    Cerebellar damage can result in improved motor coordination.

    <p>False</p> Signup and view all the answers

    What is proprioception?

    <p>The sense of body position.</p> Signup and view all the answers

    The brainstem integrates information to adjust motor commands based on ______ input.

    <p>sensory</p> Signup and view all the answers

    What type of movements do specialized neural pathways handle?

    <p>Both reflexive and learned actions</p> Signup and view all the answers

    What is the primary function of the stabilizer muscle during movement?

    <p>To hold a body part in place during movement</p> Signup and view all the answers

    Which statement accurately describes the role of rate coding in muscle function?

    <p>It increases the firing rate of already active motor units</p> Signup and view all the answers

    In trained individuals, how does intramuscular coordination generally compare to untrained individuals?

    <p>Agonists are more active while antagonists are less active during task execution</p> Signup and view all the answers

    What is the main impact of muscle morphology on compartmentalization within a muscle?

    <p>It affects how compartments respond during various tasks</p> Signup and view all the answers

    How does electromyography (EMG) contribute to understanding muscle efficiency?

    <p>It evaluates the electrical activity of muscles during contraction</p> Signup and view all the answers

    What is a characteristic of how motor units behave during maximal force tasks?

    <p>Motor units are activated in a synchronous pattern</p> Signup and view all the answers

    What primary factor influences the recruitment of motor units in small muscles?

    <p>The percentage of maximal contraction required</p> Signup and view all the answers

    Which muscle fiber type primarily influences compartmentalization regarding their activation based on load?

    <p>Type II muscle fibers</p> Signup and view all the answers

    What is the primary focus of intramuscular coordination?

    <p>The cooperation of motor units within a single muscle</p> Signup and view all the answers

    What happens to movement efficiency in untrained individuals due to their muscle characteristics?

    <p>They activate antagonists excessively, hindering movement</p> Signup and view all the answers

    What is a key outcome of strength and power training?

    <p>Increased force output</p> Signup and view all the answers

    How does intermuscular coordination enhance performance during sprinting?

    <p>Through effective synchronization between agonists and antagonists</p> Signup and view all the answers

    What does intramuscular coordination primarily involve?

    <p>Synchronized firing of motor units within a single muscle</p> Signup and view all the answers

    What role do stabilizer muscles play in weightlifting?

    <p>They maintain body steady during the lifting motion</p> Signup and view all the answers

    What adaptation occurs to motor units as a result of strength training?

    <p>Earlier recruitment of high-threshold motor units</p> Signup and view all the answers

    What does optimal agonist activation contribute to?

    <p>Enhanced intermuscular coordination</p> Signup and view all the answers

    Which of the following describes a feature of intermuscular coordination?

    <p>Integration of movements among different muscle groups</p> Signup and view all the answers

    What effect does enhancing motor unit firing rates have on strength and power training outcomes?

    <p>Leads to quicker attainment of high firing rates for force development</p> Signup and view all the answers

    What is an implication of optimizing both intermuscular and intramuscular coordination?

    <p>It enhances performance in sports and functional movements</p> Signup and view all the answers

    In the context of sprinting, what role does early recruitment of high-threshold motor units in quadriceps serve?

    <p>It enables the generation of explosive power</p> Signup and view all the answers

    Match the types of muscle coordination with their definitions:

    <p>Intermuscular Coordination = Coordination of multiple muscle groups to perform a task Intramuscular Coordination = Coordination within a single muscle's motor units Motor Unit Recruitment = Activating more motor units as force demand increases Rate Coding = Increasing the firing rate of active motor units for additional force</p> Signup and view all the answers

    Match the roles of muscles with their definitions:

    <p>Agonist = Primary muscle performing the movement Antagonist = Opposes the agonist to control the movement Stabilizer = Holds a body part in place during movement Neutralizer = Counters unwanted movements from other muscles</p> Signup and view all the answers

    Match the measurement techniques with their purposes:

    <p>Electromyography (EMG) = Detects muscle electrical activity Biomechanical Efficiency = Evaluates coordination to minimize energy waste Motor Unit Firing Rate = Refers to increasing activity for higher force Compartmentalization = Division of muscle fibers into controlled compartments</p> Signup and view all the answers

    Match the muscle types with their characteristics regarding recruitment:

    <p>Small Muscles = Full recruitment at ~30% Maximal Contraction Large Muscles = Recruitment dominates until ~80-90% Maximal Contraction Fast-Twitch Fibers = Primarily involved in maximal force generation Slow-Twitch Fibers = Primarily support endurance activities</p> Signup and view all the answers

    Match the aspects of training adaptation with their effects:

    <p>Untrained Individuals = Exhibit less coordination and efficiency Trained Individuals = Demonstrate better synchronization between muscle groups Overactivation of Antagonists = Reduces movement efficiency in untrained Agonist Activity = More active in trained individuals during tasks</p> Signup and view all the answers

    Match the aspects of discharge patterning with their applications:

    <p>Smooth Contractions = Motor units alternate to maintain steady force Maximal Force = Motor units fire synchronously for maximum output High-Intensity Tasks = Require synchronous firing of motor units Most Tasks = Benefit from alternating motor unit activity</p> Signup and view all the answers

    Match the factors influencing compartmentalization of muscles:

    <p>Muscle Morphology = Type II vs Type I fiber differentiation Neural Recruitment = Specific compartments activate for specific tasks Biomechanical Function = Activation varies with movement angle Influence of Load = Different compartments respond based on load</p> Signup and view all the answers

    Match the muscle roles in movement with examples:

    <p>Agonist = Biceps during arm flexion Antagonist = Triceps during arm flexion Stabilizer = Core muscles during weightlifting Neutralizer = Counteracting wrist movement with gripping</p> Signup and view all the answers

    Match the concepts of coordination with their areas of focus:

    <p>Intermuscular Coordination = Involves multiple muscle groups Intramuscular Coordination = Involves motor units within a single muscle Training Adaptations = Changes in coordination due to experience Compartmentalization = Independence of muscle fibers within muscle</p> Signup and view all the answers

    Match the following terms related to muscle coordination with their definitions:

    <p>Intermuscular Coordination = Coordination between different muscles Intramuscular Coordination = Motor unit recruitment and firing within a single muscle Agonist = Muscle that contracts to create movement Antagonist = Muscle that opposes the action of the agonist</p> Signup and view all the answers

    Match the following training outcomes with their characteristics:

    <p>Increased force output = Improved capability to exert power Improved movement efficiency = Reduction in unnecessary energy expenditure Greater neuromuscular coordination = Enhanced ability to perform complex movements Earlier recruitment of high-threshold motor units = Faster ability to generate explosive power</p> Signup and view all the answers

    Match the following examples with their focus in athletic performance:

    <p>Sprinting = Intermuscular and intramuscular coordination for optimal stride efficiency Weightlifting = Stabilizing the body while executing a lift Agility drills = Enhancing rapid changes in direction Resistance training = Improving maximal force generation</p> Signup and view all the answers

    Match the following concepts from strength and power training with their explanations:

    <p>Enhanced motor unit firing rates = Allows quicker force development Maximal level of motor unit activation = Achieves 100% activation if not previously maximal Faster attainment of high firing rates = Contributes to rapid force production Reduced antagonist activity = Increases efficiency of movement execution</p> Signup and view all the answers

    Match the following muscle roles during weightlifting:

    <p>Core muscles = Stabilizers holding the body steady Gluteus maximus = Primary mover executing the lift Quadriceps = Muscles involved in leg extension during the lift Hamstrings = Antagonist muscles providing balance</p> Signup and view all the answers

    Match the following training adaptations with their expected effects:

    <p>Increased neuromuscular coordination = Leads to better performance in sports Quicker attainment of high firing rates = Facilitates explosive movements Earlier recruitment of motor units = Contributes to enhanced strength Greater movement efficiency = Allows for more effective energy use</p> Signup and view all the answers

    Match the following terms to their context in training applications:

    <p>Intermuscular coordination = Optimizing muscle teamwork during sprinting Intramuscular coordination = Synchronized firing within a muscle High-threshold motor units = Crucial for generating force quickly Stabilizer muscles = Ensure posture and stability during lifts</p> Signup and view all the answers

    Match the following phrases related to motor unit behavior with their significance:

    <p>Earlier recruitment = Allows for explosive power during high-intensity activities Synchronized firing = Improves overall strength and power output Maximal activation = Essential for achieving peak performance levels Motor unit firing rates = Influence the speed of muscle contraction</p> Signup and view all the answers

    Match the application of muscle coordination with its corresponding sport.

    <p>Sprinting = Requires coordination between quadriceps and hamstrings Weightlifting = Involves stabilization of core while lifting Football = Demands intermuscular coordination in agility training Basketball = Requires quick intramuscular adjustments in take-offs</p> Signup and view all the answers

    What is the primary role of the agonist muscle during movement?

    <p>To perform the primary movement</p> Signup and view all the answers

    Which factor primarily affects motor unit recruitment in small muscles?

    <p>Maximal contraction threshold</p> Signup and view all the answers

    How does compartmentalization within muscle fibers influence movement?

    <p>Allows specific fibers to activate based on task demands</p> Signup and view all the answers

    What measurement technique is used to evaluate muscle efficiency and activation patterns?

    <p>Electromyography (EMG)</p> Signup and view all the answers

    What adaptation occurs in trained individuals regarding the antagonist muscles?

    <p>Decreased activation during tasks</p> Signup and view all the answers

    Which type of muscle fibers are primarily fast-twitch fibers?

    <p>Type IIb fibers</p> Signup and view all the answers

    What is a key characteristic of discharge patterning during maximal force tasks?

    <p>Motor units activate in a synchronized manner</p> Signup and view all the answers

    Which factor predominantly influences the coordination of motor units in large muscles at high forces?

    <p>Motor unit recruitment</p> Signup and view all the answers

    What impact does having a well-coordinated intermuscular system have on performance?

    <p>Enhances overall athletic performance</p> Signup and view all the answers

    What function does the stabilizer muscle serve during dynamic activities?

    <p>To stabilize a body part for efficient movement</p> Signup and view all the answers

    What is the effect of strength and power training on motor unit activation?

    <p>It increases the maximal level of motor unit activation to 100%.</p> Signup and view all the answers

    Which of the following best describes intermuscular coordination during sprinting?

    <p>Agonists and antagonists work together for optimal stride efficiency.</p> Signup and view all the answers

    How does intermuscular coordination improve during weightlifting?

    <p>By synchronizing the firing of stabilizers and primary movers.</p> Signup and view all the answers

    What is an outcome of enhanced motor unit firing rates in strength training?

    <p>Earlier recruitment of high-threshold motor units.</p> Signup and view all the answers

    Which of the following adaptations occurs as a result of strength training?

    <p>Improved movement efficiency.</p> Signup and view all the answers

    What role do stabilizers play during weightlifting?

    <p>They hold the body steady while lifting.</p> Signup and view all the answers

    What is the relationship between strength and power training and force output?

    <p>It leads to increased force output.</p> Signup and view all the answers

    What does optimizing agonist activation contribute to in movement?

    <p>Elevated intramuscular coordination.</p> Signup and view all the answers

    In the context of sprinting, what advantages are gained from early recruitment of high-threshold motor units in the quadriceps?

    <p>It enhances explosive power.</p> Signup and view all the answers

    How does strength and power training change motor unit activation levels and recruitment patterns?

    <p>Strength and power training increases motor unit activation levels to 100% and leads to earlier recruitment of high-threshold motor units.</p> Signup and view all the answers

    What is the significance of intermuscular coordination during sprinting?

    <p>Intermuscular coordination during sprinting ensures optimal cooperation between agonist and antagonist muscles to enhance stride efficiency.</p> Signup and view all the answers

    In weightlifting, what role do stabilizer muscles play?

    <p>Stabilizer muscles maintain body stability while primary movers execute the lift, enabling safe and effective performance.</p> Signup and view all the answers

    Explain the role of feedback in closed-loop control systems during human movement.

    <p>Feedback in closed-loop control systems allows for real-time error detection and correction to achieve desired movement goals.</p> Signup and view all the answers

    Why are rapid, discrete tasks challenging for closed-loop control models?

    <p>Rapid, discrete tasks are challenging for closed-loop control because there isn’t enough time to process feedback before the movement is completed.</p> Signup and view all the answers

    Describe how open-loop control differs from closed-loop control in movement execution.

    <p>Open-loop control involves predetermined instructions executed without feedback, while closed-loop control incorporates feedback for adjustments.</p> Signup and view all the answers

    What adaptations occur in the firing rates of motor units as a result of strength training?

    <p>Strength training enhances motor unit firing rates, allowing for quicker attainment of high firing rates for rapid force development.</p> Signup and view all the answers

    What outcomes can be expected from improving neuromuscular coordination through training?

    <p>Improving neuromuscular coordination through training can lead to increased force output and improved movement efficiency.</p> Signup and view all the answers

    How does proprioceptive feedback contribute to movement corrections in closed-loop systems?

    <p>Proprioceptive feedback provides critical information about body position, enabling the executive system to make adjustments for movement accuracy.</p> Signup and view all the answers

    How does the role of stabilizer muscles differ from that of agonist muscles during movement?

    <p>Stabilizer muscles support and hold a body part in place, while agonist muscles are the primary movers performing the movement.</p> Signup and view all the answers

    What is the primary effect of session training on intermuscular coordination in trained individuals?

    <p>Trained individuals show better synchronization between agonists and antagonists, leading to improved movement efficiency.</p> Signup and view all the answers

    Explain the concept of rate coding in the context of intramuscular coordination.

    <p>Rate coding involves increasing the firing rate of active motor units to produce additional force, predominating in high force demands.</p> Signup and view all the answers

    How does compartmentalization within muscles influence their biomechanical function?

    <p>Compartmentalization allows for the independent activation of specific muscle groups, enhancing functional adaptability based on task demands.</p> Signup and view all the answers

    What is the relationship between motor unit recruitment and firing rate in large and small muscles?

    <p>In small muscles, full recruitment occurs at lower force levels while large muscles rely on recruitment for lower to moderate forces, shifting to rate coding for higher forces.</p> Signup and view all the answers

    Describe how EMG is used to measure muscle efficiency.

    <p>Electromyography (EMG) detects electrical activity in muscles to assess the activation patterns of agonists and antagonists, indicating efficiency.</p> Signup and view all the answers

    What are the implications of having an overactive antagonist in untrained individuals?

    <p>An overactive antagonist can reduce movement efficiency by opposing the agonist's actions, leading to inefficient performance.</p> Signup and view all the answers

    How does the firing pattern of motor units change during maximal force outputs?

    <p>During maximal force tasks, motor units typically fire synchronously to generate a greater force output.</p> Signup and view all the answers

    Explain the significance of biomechanical efficiency in muscle coordination.

    <p>Biomechanical efficiency evaluates how effectively muscles work together to minimize energy waste during movement.</p> Signup and view all the answers

    Why is motor unit recruitment predominant in the low force range for small muscles?

    <p>Small muscles achieve necessary force through full motor unit recruitment, activating most motor units at lower intensity levels.</p> Signup and view all the answers

    What primarily influences how motor units are recruited in small muscles?

    <p>Muscle morphology and neural recruitment patterns</p> Signup and view all the answers

    Which muscle fiber type is predominantly recruited during high-intensity tasks requiring maximal force output?

    <p>Type II (fast-twitch) fibers</p> Signup and view all the answers

    How does compartmentalization within a muscle influence its function?

    <p>By segregating muscle fibers for specialized tasks</p> Signup and view all the answers

    What role do antagonistic muscles play in intermuscular coordination?

    <p>They help decelerate and control movements</p> Signup and view all the answers

    In what phase of recruitment do larger muscles primarily activate motor units?

    <p>At maximal contraction levels</p> Signup and view all the answers

    During smooth contractions, how do motor units typically operate?

    <p>Motor units alternate their activity</p> Signup and view all the answers

    What is the primary measurement focus of electromyography (EMG) in assessing muscle performance?

    <p>Muscle electrical activity and activation patterns</p> Signup and view all the answers

    What is a significant characteristic of trained individuals compared to untrained individuals regarding intermuscular coordination?

    <p>Enhanced synchronization of agonists and antagonists</p> Signup and view all the answers

    Which factors most influence the firing rate of motor units in high force production tasks?

    <p>The balance between rate coding and recruitment</p> Signup and view all the answers

    What impacts biomechanical efficiency in relation to muscle coordination?

    <p>Proper synchronization between muscle groups</p> Signup and view all the answers

    Which of the following accurately describes the role of intermuscular coordination during weightlifting?

    <p>Primary movers execute the lift while stabilizers maintain body position.</p> Signup and view all the answers

    What is the primary function of closed-loop control in the context of human performance?

    <p>To integrate feedback for real-time movement correction.</p> Signup and view all the answers

    What distinguishes intramuscular coordination from intermuscular coordination?

    <p>Intramuscular coordination focuses on recruitment within a single muscle.</p> Signup and view all the answers

    Which adaptation occurs to motor units as a direct result of strength and power training?

    <p>Increased maximal activation levels up to 100%.</p> Signup and view all the answers

    Which statement best describes open-loop control systems?

    <p>They operate without feedback and cannot correct errors.</p> Signup and view all the answers

    What is a limitation of closed-loop control models in terms of reaction time?

    <p>They are slow due to feedback processing constraints.</p> Signup and view all the answers

    In the context of sprinting, what is the role of high-threshold motor unit recruitment?

    <p>To generate explosive power by early activation.</p> Signup and view all the answers

    How does enhanced motor unit firing rates directly influence strength training outcomes?

    <p>It supports faster force development.</p> Signup and view all the answers

    What is a characteristic feature of feedback in closed-loop control systems?

    <p>It is used for error detection and correction.</p> Signup and view all the answers

    What is the impact of optimizing both intermuscular and intramuscular coordination?

    <p>It enhances performance in sports and functional movements.</p> Signup and view all the answers

    Study Notes

    Central Neural Mechanisms in Planning and Initiating Movement

    • Movement initiation involves a complex interplay between various brain regions, including the cortex, basal ganglia, cerebellum, and brainstem.

    • The motor cortex is crucial for planning and executing voluntary movements. Different areas within the motor cortex are specialized for controlling specific muscle groups and body parts.

    • The premotor cortex plays a critical role in planning and sequencing movements, receiving input from areas involved in sensory processing and higher-level cognitive functions.

    • The supplementary motor area (SMA) is also involved in planning, particularly for complex, internally generated movements. It also plays a role in the initiation and coordination of sequences.

    • The basal ganglia are a group of interconnected subcortical nuclei that play multifaceted roles in motor control, including regulating the force and speed of movements, inhibiting unwanted movements, and contributing to the initiation of actions. Parkinson's disease is a neurological disorder that affects the basal ganglia, leading to motor impairments.

    • The cerebellum is vital for motor learning, coordination, and error correction during movement execution. It receives sensory feedback from the body and the motor commands from the cortex to refine and adjust ongoing motions. Cerebellar damage can result in impaired motor coordination and balance.

    • The brainstem contains essential motor nuclei that control vital reflexes, posture, and muscle tone. Many cranial nerves originate in the brainstem and control eye movements, facial expressions, and other cranial muscles. The brainstem integrates information from numerous cortical and subcortical sources to adjust motor commands based on sensory input.

    • Planning and initiation of movement require the integration of sensory information, such as proprioception (sense of body position) and vestibular input (balance). Processing this information allows the brain to create appropriate motor commands.

    • Motor plans can be influenced by various cognitive factors such as motivation, attention, and decision-making processes. Higher-level cognitive functions interact with the motor system to adjust movement strategies based on current context and goals.

    • Neural pathways for different types of movements are specialized, some for simple, reflexive actions and others for intricate, learned actions.

    • Individual neural circuits form complex networks that generate specific patterns of muscle activity.

    • Sensory feedback loops play a crucial part in the continuous adjustment of movements. The brain constantly processes sensory information to refine motor commands and adapt to changing conditions.

    • Motor learning involves changes in neural circuits, allowing for improved motor performance over time. Practice strengthens synaptic connections and refines motor control.

    • Neurotransmitters, such as dopamine, play critical roles in modulating movement initiation and control. Imbalances in neurotransmitter systems can impact motor functions.

    Specific Neural Pathways

    • Direct pathway: A relatively direct pathway from the motor cortex to the spinal cord for initiating quick, precise movements.

    • Indirect pathway: A more complex pathway involving several intermediate structures, such as the basal ganglia and cerebellum that influence movement, allowing for more complex and adaptable actions.

    • Sensory feedback pathways: These pathways provide constant sensory information about the body's position and movement, allowing for corrections and adjustments.

    Disorders Affecting Movement

    • Neurological disorders, such as Parkinson's disease, Huntington's disease, and cerebellar ataxia, disrupt the normal functioning of these neural mechanisms, leading to various motor impairments.

    • Stroke can also result in deficits in movement initiation and execution in affected limbs, often requiring rehabilitation protocols to regain lost function.

    • 1. Intermuscular Coordination

      • Definition: The coordination of multiple muscle groups and body segments to perform a task efficiently and effectively.
      • Roles of Muscles:
        • Agonist: The primary muscle performing the movement.
        • Antagonist: Opposes the agonist to control or decelerate the movement.
        • Stabilizer: Holds a body part in place to allow the primary movement.
        • Neutralizer: Counters unwanted movements caused by other muscles.

      Key Measurements:

      • Electromyography (EMG):
        • Detects muscle electrical activity (muscle action potential) using surface or inserted electrodes.
        • Measures efficiency and activation patterns of agonists and antagonists.
      • Biomechanical Efficiency:
        • Evaluates how effectively muscles coordinate to minimize energy waste.

      Training Adaptations:

      • Untrained individuals exhibit less coordination:
        • Overactivation of antagonists reduces movement efficiency.
      • Trained individuals demonstrate better synchronization between agonists and antagonists:
        • Agonists are more active, and antagonists are less active during task execution.

      2. Intramuscular Coordination

      • Definition: The coordination within a single muscle, focusing on how motor units (MUs) work together to produce force.

      a. Motor Unit Recruitment and Firing Rate:

      • Recruitment:
        • Involves activating more motor units as force demand increases.
        • Predominates in the low force range.
      • Rate Coding:
        • Refers to increasing the firing rate of active motor units for additional force.
        • Predominates in the high force range.
      • Factors Affecting Recruitment vs. Rate Coding:
        • Small Muscles (e.g., hands): Full MU recruitment at ~30% Maximal Contraction (MC), relying on rate coding for higher forces.
        • Large Muscles (e.g., quadriceps): Recruitment dominates until ~80-90% MC.

      b. Discharge Patterning:

      • Smooth Contractions (Most Tasks):
        • Motor units alternate activity to maintain steady force and prevent fatigue.
      • Maximal Force (High-Intensity Tasks):
        • Motor units fire synchronously to generate maximum force output.

      c. Compartmentalization:

      • Definition: Division of muscle fibers into smaller, independently controlled compartments within a single muscle.
      • Factors Influencing Compartmentalization:
        • Muscle Morphology: Fast-twitch (Type II) vs. slow-twitch (Type I) fibers.
        • Neural Recruitment: Specific compartments activate during specific tasks.
        • Biomechanical Function: Compartments may vary in activation based on movement angle or load.
      • Example: The deltoid muscle compartments:
        • Anterior: Active during flexion.
        • Medial: Active during abduction.
        • Posterior: Active during extension.

      3. Adaptations of Motor Unit Behavior to Training

      • Strength and Power Training:
        • Increases the maximal level of motor unit activation to 100% if not previously maximal.
        • Enhances motor unit firing rates.
        • Causes earlier recruitment of high-threshold motor units.
        • Enables quicker attainment of high firing rates for faster force development.
      • Outcomes of Training:
        • Increased force output.
        • Improved movement efficiency.
        • Greater neuromuscular coordination.

      4. Applications

      Example 1: Sprinting

      • Intermuscular Coordination: Agonists (quadriceps) and antagonists (hamstrings) work together for optimal stride efficiency.
      • Intramuscular Coordination: High-threshold motor units in the quadriceps are recruited early to generate explosive power.

      Example 2: Weightlifting

      • Intermuscular Coordination: Stabilizers (core muscles) hold the body steady while primary movers (e.g., gluteus maximus) execute the lift.
      • Intramuscular Coordination: Synchronized firing of motor units enhances strength and power during the lift.

      Key Takeaways

      1. Intermuscular Coordination:

        • Focuses on coordination between different muscles.
        • Enhanced by reducing unnecessary antagonist activity and optimizing agonist activation.

      2. Intramuscular Coordination:

        • Focuses on motor unit recruitment and firing within a single muscle.
        • Improved through strength and power training, leading to faster and more powerful contractions.

      3. Practical Implication:

        • Optimizing both intermuscular and intramuscular coordination is crucial for enhancing performance in sports and functional movements​(PHYL4518 - Wk5 - Oct 2 …).

        Major Roles of Open-Loop Organizations
        • Determine which muscles contract
        when, how forcefully, and for how long
        • To organize the many degrees of
        freedom of the muscles and joints into a
        single unit
        • To determine postural adjustments
        necessary to support the upcoming
        action
        • E.g. bicep pull experiment
        • To modulate the many reflex pathways
        to ensure that the movement goal is
        achieved

        Control of Movement:
        Open-loop vs. closed loop
        • Two ways in which movements could be controlled
        • Open-Loop Control: A type of system control in which instructions for the
        effector system are determined in advance and run off without feedback
        • Closed loop Control: A type of system control involving feedback, error
        detection, and error correction that is applicable to maintaining a system
        goal.

        Closed-Loop Control Systems:
        General Concept Example
        • Desired state is set (20oC)
        • Sensory information measured and compared
        to expected temperature
        • Any difference detected as error (e.g. too
        cold)
        • Error transmitted to executive to decide what
        to do to eliminate error (e.g. decide to turn on
        furnace)
        • Command sent to effector (furnace turns on)
        • The action returns the system to the desired
        state (20oC)
        • This information is sent to the executive, and
        the cycle continues (e.g. furnace turns on and
        off all day to maintain house temperature)
        Desired state:
        20oC
        Executive
        System
        Effector
        System
        Comparato
        r
        Actual state
        Error
        Sensory info
        Negative feedback loop!

        Closed-Loop Control in Human
        Performance
        • Reaching to pick up cup
        • Visual info about hand’s position relative to cup
        represents feedback (i.e. information about the
        movement outcome)
        • Difference in hand location and desired location
        represent errors
        • Executive determines correction and modifies an
        effector
        • Most movements have several feedback
        sources

        Closed-Loop Control in Human
        Performance
        Input
        Stimulus
        Identification
        Response
        Selection
        Movement
        Programmin
        g
        Motor
        Program
        Spinal Cord
        Movement
        Comparator
        Error
        Exteroceptive feedback
        Proprioceptive feedback
        Muscles

        Input
        Stimulus
        Identification
        Response
        Selection
        Motor
        Program
        Spinal Cord
        Movement
        Comparator
        Error
        Exteroceptive feedback
        Proprioceptive feedback
        Muscles
        Closed-Loop Control: Feedforward
        Anticipated feedback
        Movement
        Programmin
        g

        Closed-Loop Control: Feedforward
        • Anticipated feedback (also called
        feedforward info)
        • Sensory consequences that are
        expected to arise
        • Why can’t you tickle yourself?
        • If anticipated feedback matches
        actual feedback, then there is
        diminished perception of sensation
        • Example 2: Force escalation
        between siblings
        • Shergill et al., 2003
        • 38% increase in force between each
        turn

        Limitations of Closed-Loop Control
        Models
        • 1. Very Slow
        • Feedback must be sent to executive,
        and information must be processed
        (seen as reaction time)
        • Example: Tracking tasks (follow a
        moving target)
        • Only about 3 corrections per second are
        possible
        • E.g. bouncing football is hard to grab

        Limitations of Closed-Loop Control
        Models
        • 2. Rapid, discrete tasks would be impossible
        under this model
        • E.g. texting, playing guitar
        • These movements occur too quickly to process info
        before the movement is complete
        • Therefore, these movements must be programed in
        advance

        Motor Program Theory:
        Closed-Loop and Open Loop Control
        • Closed loop = Open loop with feedback
        • In most tasks, motor behavior is neither
        open- nor closed-loop alone but a
        complex blend of the two
        • Slow movements  Control dominated by
        feedback
        • Fast/brief movements  Open-loop
        dominates

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    Explore the complex interactions of various brain regions involved in planning and initiating movement. This quiz covers the roles of the motor cortex, premotor cortex, supplementary motor area, and basal ganglia in motor control.

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